1. Field of the Invention
The present invention relates to an image recording apparatus in which a recording head reciprocates together with a carriage in main scanning directions to perform an image recording, and particularly relates to an image recording apparatus in which an output of a driving motor is selectively transmitted to a plurality of driving portions.
2. Description of Related Art
An ink jet printer is known as an image recording apparatus which performs an image recording by selectively ejecting an ink from a recording head onto a recording medium in a conveyance of a recording sheet from a sheet supply tray to a sheet discharged tray. The recording sheet is supplied from the sheet supply tray to a sheet conveying path, and is conveyed in the sheet conveying path. The supply and the conveyance are carried out by that rollers, such as sheet supply rollers and conveyance rollers, are brought into contact with the recording sheet, pressed onto the recording sheet, and rotated. As a drive source for these rollers, a motor, such as a DC motor and a stepping motor, is used. A transmission of driving from the motor to the rollers is achieved by a drive transmission mechanism having a combination of a pinion gear and a timing belt.
Regarding a recording head used in the ink-jet printer, an air bubble may generate in a nozzle which ejects an ink, and a foreign matter may clog up the nozzle. These incidents cause an ejection failure of the ink. A procedure is known for a prevention for and a recover from the ejection failure of the ink. According to the procedure, the air bubble and the foreign matter will be sucked to be removed from the nozzle of the recording head. This procedure is commonly referred to as a purge. A maintenance unit for performing the purge includes a cap covering the nozzle of the recording head, a pump for decreasing a pressure in the cap, and so on. The motor is also used for driving the pump in the maintenance unit, used as a drive source for a cam for switching an exhaust valve, and so on. A transmission of driving from the motor to each of drive portions is achieved by the aforementioned drive transmission mechanism.
An image recording apparatus having a drive transmission switching device is conventionally known. The drive transmission switching device switches a transmission of a driving from the motor as the drive source to each of the drive portions. The drive transmission switching device selectively transmits the driving to each of the drive portions in accordance with a movement position of the carriage. Therefore, the single drive source can transmit the driving, for example, to the conveyance roller in the image recording and to the maintenance unit in the purge.